Adhesive compositions



Patented July 3, 1945 ADHESIVE COMPOSITIONS Jan Teppema, Cambridge, andJoseph F. Manning, Boston, Mass., assignors to B. B. Chemical 00.,Boston, Mass., a corporation of Massachusetts P No Drawing- ApplicationJuly 2, 1943,

Serial No. 493,298

3 Claims.

This invention relates to liquid adhesive compositions embodyingbutadiene-acrylonitrile copolymer and more particularly tosuch adhesivesadvantageous for securing together leather and shoe parts.

Butadiene-acrylonitrile copolymer may be obtained commercially in theform known as Hycar (Type O. R.) manufactured by the Hycar ChemicalCompany, Akron, Ohio. The material Hycar is plastic in the sense that itmay be worked on the rolls of a rubber mill and compounded with otheringredients in a manner similar to that in which crude rubber istreated. Such copolymer of butadiene-acrylonitrile may be cured orvulcanized to a condition in which it is elastic rather than plastic andin which condition it resembles vulcanized rubber. This curing isprobably a further polymerization of the plastic copolymer to asubstantially fully polymerized condition rather than the addition ofsulphur to the polymer such as is considered to occur in thevulcanization of rubber. The commercial copolymers contain approximately75% by weight of butadiene and 25% of acrylonitrile. Similar copolymersmay also be obtained commercially under the trade name "Chemigummanufactured by Goodyear Tire 8; Rubber Co., Akron, Ohio, or under thetrade name Perbunan manufactured by the Standard Oil Company of NewJersey.

From their general similarity to neoprene as synthetic rubber-likematerial it might be supposed that such butadiene-acrylonitrilecopolymers would be suitable as an adhesive medium, for example in theattachment of outsoles to shoe uppers in the manufacture of shoes. Such,however, is not the case. When the butadieneacrylonitrile copolymer isemployed for the attachment of an outsole to a shoe upper, the resultingadhesive bond is unsatisfactory. The adhesive bond is soft and stretchy,and the parts are not held closely together.

and other 1 objects are attained by liquid adhesive compositionscomprising butadieneacrylonitrile copolymer in association with atoughener. for the copolymer consisting of,

pyroxylin. The butadiene-acrylonitrile copolymer and pyroxylin aredispersed in a solvent.

In the composition the ratio by weight of the pyroxylin andbutadiene-acrylonitrile copolymer may range from 1:2 to 2:1, and apreferred ratio is 1:1. The composition may and preferably does containcompounding and modifying ingredients,

and in order to promote curing of the butadieneacrylonitrile copolymerat temperatures in the neighborhood of room temperature, an acceleratormay be associated with the composition.

The advantages of the invention are particularly apparent when adhesivecompositions in accordance therewith are employed in the attaching'ofoutsoles to shoe uppers. Compositions according to the invention providean adhesive bond which is strong and wherein the shoe parts are heldtightly together without gaping.

A specific example of a preferred composition in accordance with thisinvention is as follows:

Parts by weight Butadiene-acrylonitrile copolymer (Hycar, type 0. R.) l

Pyroxylin (6 seconds viscosity) 100 Sulphur 2 Stearic acid 1.5 Zincoxide 5 Calcium silicate (Silene) 2i) Butyl Eight (accelerator) 0.25Ethyl alcohol 35 Ethyl acetate 350 Methyl ethyl ketone 400 The abovecomposition may be prepared by milling the butadiene-acrylonitrilecopolymer for a period of about 15 to 20 minutes. The sulphur, zincoxide, calcium silicate and stearic acid then may be associated with thebutadiene-acrylonitrile copolymer on the mill, and the milling may becontinued for 10 or more minutes longer. The compounded material maythen be cut into small pieces and placed in a chum with the solvent, andthe churning continued for a substantial period of time, for exampleeight hours. The pyroxylin and butyl eight may be added to the materialin the churn. Conveniently the pyroxylin may be added in the form'of asolution thereof in ethyl alcohol and ethyl acetate.

In the above composition the butadieneacrylonitrile copolymer is theadhesive material and the pyroxylin is a toughener therefor. Pyroxylin(nitrocellulose) is marketed by the Hercules Powder 00., Wilmington,Delaware, and may be obtained and employed in any of a wide range ofviscosity characteristics. The stearic acid aids in processing thebutadiene-acrylonitrile copolymer. The sulphur and zinc oxide assist inthe curing of the butadiene-acrylonitrile copolymer. Silene (calciumsilicate) is a filler and reinforcer. Butyl eight is an accelerator ofvulcanization and methyl ethyl ketone is a solvent. The solvent ispreferably employed in such amount that the total ofbutadiene-acrylonitrile' copolymer and pyroxylin will be from to byweight of the total composition.

The dispersions or colloidal solutions of a butadiene acrylonitrilecopolymer and pyroxylin toughener of this invention may vary widely incomposition and may consist of the copolymer and toughener and solventwithout additional compounding ingredients.

In carrying out the adhesion of leather or shoe parts by means of liquidadhesive composition of this invention the parts, for example an outsoleand shoe upper, are mechanically prepared for sole attaching preferablyby roughing the attaching surfaces thereof in a suitable manner, such asby an emery wheel or a wire brush, in order to provide surfaces mostadvantageous for cementing. The liquid adhesive composition containingthe butadiene-acrylonitrile copolymer and toughener is then appliedpreferably to both surfaces to be united. The application of theadhesive may be by brush, by extrusion or in any other suitable manner.The applied liquid adhesive composition is then permitted partially todry whereby copolymer-toughener films are deposited on the respectiveattaching surfaces and an chored securely to the substance of theoutsole and upper respectively.

While the coplymer-toughener is in adhesive condition, which may bewithin about 10 or 15 minutes after the application of the liquidadhesive composition to the outsole and shoe upper, the outsole and hoeupper are pressed together with the attaching surfaces in juxtaposition.The outsole and shoe upper may be maintained under sole attachingpressure for about 15 to seconds. An attaching pressure of pounds persquare inch has been found satisfactory.

butadiene-acrylonitrile copolymer containing in the neighborhood of 25%by weight of acrylonitrile dispersed in a solvent for said copolymer,and a toughener for the coplymer consisting of pyroxylin, the ratio byweight of the pyroxylin and butadiene-acrylonitrile -copolymer beingfrom 1:2to2z1.

2. A liquid adhesive composition comprising butadiene-acrylonitrilecopolymer containing in the neighborhood of 25% by weight ofacrylonitrile, and a toughener for said copolymer consisting ofpyroxylin in amount by weight approximately equal to that of thecopolymer, said copolymer and pyroxylin being dispersed in a solvent.

3. A liquid adhesive composition for securing together parts of leatheror other material, said material comprising the following ingredients inapproximately the following proportions by weight:

- Parts Butadiene-acrylonitrile copolymer containing in the neighborhoodof 25% by weight of acrylonitrile Pyroxylin 100 Stearic acid 1.5 Zinoxide 5 Sulphur v 2 Calcium silicate 20 Solvent 600 to 800 JAN TEPPEMA.

JOSEPH F. MANNING.

